Process for the production of paper

Abstract

A process for the production of paper from a suspension of cellulose containing fibers, and optional fillers, which comprises adding an aluminum compound and anionic inorganic particles to the suspension, forming and draining the suspension on a wire, wherein the aluminum compound and anionic inorganic particles are mixed immediately prior to addition to the suspension.

We claim: 
     
       1. A process for the production of paper which comprises a) providing an aqueous suspension containing cellulose fibers and optional fillers;   b) adding to said suspension i) at least 0.05 kg/ton, calculated as dry polymer on dry fibers and optional fillers, of cationic starch,   ii) at least 0.001 kg/ton, calculated as Al 2  O 3  based on dry fibers and optional fillers of an aluminum compound selected from the group consisting of alum, aluminates, aluminum chloride, aluminum nitrate, polyaluminum compounds and mixtures thereof,   iii) at least 0.01 kg/ton, calculated as dry particles on dry fibers and optional fillers of anionic inorganic particles, wherein said aluminum compound and said anionic inorganic particles are mixed immediately prior to being added to said suspension and wherein said anionic inorganic particles are selected from the group consisting of colloidal silica, polysilicic acid, colloidal aluminum-modified silica having a specific surface area up to 1000 m 2  /g, bentonite, and mixtures thereof and;     c) forming and draining the obtained suspension on a wire.   
     
     
       2. The process of claim 1, wherein the aluminum compound is mixed with the anionic inorganic particles less than 1 minute before adding the resultant mixture to the suspension. 
     
     
       3. The process of 1, wherein an aqueous stream of the aluminum compound is brought into contact with an aqueous stream of the anionic inorganic particles and the resulting aqueous stream is introduced into the suspension. 
     
     
       4. The process of claim 1, wherein the aluminum compound is alum, aluminate, aluminum chloride, aluminum nitrate, polyaluminum chloride, polyaluminum sulphate, polyaluminum chloride containing sulphate or polyaluminum silicate-sulphate. 
     
     
       5. The process of claim 1, wherein the anionic inorganic particles are colloidal silica, polysilicic acid or colloidal aluminum-modified silica. 
     
     
       6. The process of claim 5, wherein the anionic inorganic particles are colloidal silica or colloidal aluminum-modified silica, the particles having a specific surface area within the range of from 50 to 1000 m 2  /g. 
     
     
       7. The process of claim 5, wherein the anionic inorganic particles are polysilicic acid with a specific surface area within the range of from 1000 to 1700 m 2  /g. 
     
     
       8. The process of claim 1, wherein the anionic inorganic particles originate from a silica sol having an S-value within the range of from 8 to 45% containing silica particles with a specific surface area within the range from 750 to 1000 m 2  /g, the particles being aluminum-modified to a degree of from 2 to 25%. 
     
     
       9. The process of claim 1, wherein the anionic inorganic particles are silica based particles and bentonite. 
     
     
       10. The process of claim 1, wherein the weight ratio of anionic inorganic particles to aluminum compound is within the range of from 100:1 to 1:1. 
     
     
       11. The process of claim 1, wherein the anionic inorganic particles are added in an amount of from 0.05 to 5 kg/ton, calculated as dry particles on dry fibers and optional fillers. 
     
     
       12. The process of claim 1, wherein the aluminum compound is added in an amount of from 0.01 to 1 kg/ton, calculated as Al 2  O 3  based on dry fibers and optional fillers. 
     
     
       13. The process of claim 1, wherein cationic starch is added to the suspension in an amount from 1 to 15 kg/ton, calculated as dry on dry fibers and optical fillers. 
     
     
       14. The process of claim 1, wherein the suspension comprises filler. 
     
     
       15. The process of claim 14 wherein the suspension contains a calcium carbonate filler. 
     
     
       16. A process for the production of paper comprising (a) providing a suspension containing cellulosic fibers and optional fillers;   (b) adding to said suspension (i) an organic polymer drainage and/or retention aid selected from cationic starch, the organic polymer being added to said suspension in an amount of at least 0.005 kg/ton, calculated as dry polymer on dry fibers and optional fillers,   (ii) at least 0.001 kg/ton, calculated as Al 2  O 3  based on dry fibers and optional fillers of an aluminum compound selected from the group consisting of alum, aluminates, aluminum chloride, aluminum nitrate, polyaluminum compounds and mixtures thereof, and   (iii) and at least 0.01 kg/ton of anionic silica-based particles having a specific surface area from 50 to 1000 m 2  /g, the amount of silica-based particles added calculated as SiO 2  on dry fibers and optional fillers, said aluminum compound and said silica-based particles being mixed immediately prior to addition to said suspension; and     (c) forming and draining the obtained suspension on a wire to form paper.   
     
     
       17. The process of claim 16, wherein the silica-based particles have a specific surface area of from 100 m 2  /g to 950 m 2  /g. 
     
     
       18. A process for the production of paper comprising (a) providing a suspension containing cellulosic fibers and optional fillers;   (b) adding to said suspension (i) as an organic polymer drainage and/or retention aid, cationic starch, the cationic starch being added to said suspension in an amount of at least 0.05 kg/ton, calculated as dry polymer on dry fibers and optional fillers,   (ii) at least 0.001 kg/ton, calculated as Al 2  O 3  based on dry fibers and optional fillers of an aluminum compound selected from the group consisting of alum, aluminates, aluminum chloride, aluminum nitrate, polyaluminum compounds and mixtures thereof, and   (iii) at least 0.01 kg/ton of a polysilicic acid having a specific surface area above about 1000 m 2  g, calculated as SiO 2  on dry fibers and optional fillers, wherein an aqueous stream of the aluminum compound is brought into contact with an aqueous stream of the polysilicic acid and the resulting aqueous stream is essentially immediately introduced into the suspension; and     (c) forming and draining the obtained suspension on a wire to form paper.